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Access pixels (I need for speed!)

Posted on 2004-04-23
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Last Modified: 2010-04-05
Hi Experts,
I want to get about 500 squares with different size from a bitmap and stretch them into 40 x 40 squares. these lines are to slow to do it:

bmp:=Tbitmap.create;
bitmap:=tbitmap.create;
strbitmap:=tbitmap;
bitmap.assign(image1.picture.bitmap);
bmp.canvas.copyrect(rect(0,0,100,100),bitmap.canvas,rect(0,0,100,100));
strbitmap.canvas.stretchdraw(rect(0,0,40,40),bitmap.canvas);

to make 500 of strbitmaps it takes more than a second. how can I make it faster. and also I want to access pixels faster - for example I want to count pixels with redvalue of 200~255. don't tell ScanLine is fast ;)
If DirectX or OpenGL are to solve it, please name some good packages which do that.
Thank U,

Comboy
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Question by:Comboy
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9 Comments
 
LVL 11

Expert Comment

by:shaneholmes
ID: 10900255
ScanLine is fast!

 <SMILE>

Shane
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Author Comment

by:Comboy
ID: 10903075
It's faster with DirectX, isn't it? Oh well, it's not fast in my case... ;)
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Expert Comment

by:Kunfufaresi
ID: 10904794
anything faster than ScanLine existed and I wasnt told??
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LVL 11

Expert Comment

by:shaneholmes
ID: 10904819
Thanks Kunfufaresi, Im not alone!

Shane
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Expert Comment

by:Kunfufaresi
ID: 10905143
you could read the bitmap into an array like 1..1000000,1..3, with RGB already seperated and work on that if you plan many operations/countings on the same bitmap.
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Expert Comment

by:Kunfufaresi
ID: 10905223
Hello,

here is a doc about scanlines optimization

http://homepages.borland.com/efg2lab/ImageProcessing/Scanline.htm#Examples

it has lots of information about scanlines, but no magic to boost the speed more than 10%, although there is a mention that if you could get access to your PCI/AGP screen card directly the speed dial would jump 10 times, but how to do that it doesnt say, guess you could reverse enginere your screen card drivers! :O

Kunfu Faresi
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LVL 11

Expert Comment

by:ZhaawZ
ID: 10906737
Hey, Comboy! don't say that ScanLines aren't fast ;) I've made color counter some time ago, that counts all used colors in 1600x1200 picture in about 30 msecs on my PC (and I used ScanLines)!
You said that you want to count pixels with redvalue of 200~255. If you need my alghorithm (you'll have to change some places in it) - just say, I'll copy it here.
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LVL 1

Author Comment

by:Comboy
ID: 10906961
Hi,
ZhaawA > is it the way you count:

var
bitmap:tbitmap;
p:pbytearray;
x,y,q,w,i:integer;
begin
bitmap:=tbitmap.Create;
bitmap.Assign(image1.Picture.Bitmap);
q:=gettickcount;
for i:=0 to 100 do begin
for x:=0 to bitmap.Height-1 do begin
p:=bitmap.ScanLine[x];
for y:=0 to bitmap.Width-1 do begin
if (p[y*3+2]>200) and (p[y*3+2]<255) then begin
p[y*3+0]:=255;
p[y*3+1]:=255;
p[y*3+2]:=255;
end;
end;
end;
end;
w:=gettickcount;
image1.Picture.Bitmap.Assign(bitmap);
showmessage:=(inttostr(w-q));
end;

Ok, image1.height is 240 and image1.width is 320. in this code I looked for 200<redvalue<255 for 100 times. it takes about 32~47 milliseconds by an ATi Radeon 7000 64MB. and 450 milliseconds for 1000 scans.
But I'm sure DirectX can increase it. If you know how to touch top speed with G32 components (or any other accelerators), please let me know.
Thanks
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Accepted Solution

by:
Kunfufaresi earned 280 total points
ID: 10907256
hello have you tried using the libraries at

http://www.ampaze.de/dx/nine/

it has directx and directdraw unit has scanline, but i've not used it before.
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